Auto merge of #22117 - asajeffrey:magicleap-ci, r=jdm

Add magicleap builder

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Add a magicleap builder to `etc/ci/buildbot_steps.yml` to gate releases on building the magicleap library. This doesn't yet check for building the magicleap app, or add a nightly release. That'll be a later PR.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because it's adding a build test

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etc/ci/buildbot_steps.yml

@@ -229,6 +229,17 @@ android-nightly:
   - ./mach upload-nightly maven
   - ./etc/ci/clean_build_artifacts.sh
 
+magicleap:
+ env:
+  MAGICLEAP_SDK: /Users/servo/magicleap/v0.17.0
+ commands:
+  - ./mach clean-nightlies --keep 3 --force
+  - ./mach clean-cargo-cache --keep 3 --force
+  - ./etc/ci/clean_build_artifacts.sh
+  - ./mach build --magicleap --dev
+  - bash ./etc/ci/lockfile_changed.sh
+  - ./etc/ci/clean_build_artifacts.sh
+
 arm32:
  env:
   AR: /usr/bin/arm-linux-gnueabihf-ar